Site preference of Zr in Heusler alloys Zr2YAl (Y = Cr, Mn, Fe, Co, Ni) and its influence on the electronic properties

Abstract

The site preference of 4d transition metal element Zr in Heusler alloys Zr2YAl (Y = Cr, Mn, Fe, Co, Ni) has been investigated theoretically. In these alloys the two Zr atoms prefer entering the A (0, 0, 0) and C (0.5, 0.5, 0.5) sites in the lattice of Heusler alloys and forming L21 structure (Cu2MnAl-type). This is different from previous predictions based on “number of valence electrons”, in which Zr atoms were predicted to occupy A (0, 0, 0) and B (0.25, 0.25, 0.25) sites and form XA (Hg2CuTi-type) structure. Present work suggests that L21 structure has a much lower total energy compared with XA type. Half-metallicity and spin gapless semiconductor character have been predicted in XA type Zr2YAl, but these properties may be disturbed under the more stable L21 structure. The energy difference between the XA and L21 structures increases as Y atom varies from Cr to Ni. The reason has been discussed based on the charge density difference. The magnetic properties of Zr2YAl have been investigated, a new possible Slater-Pauling curve of M = Z−22 has been observed in Zr2CoAl and Zr2NiAl.